State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, P. R. China.
Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States.
Anal Chem. 2020 Apr 21;92(8):5904-5909. doi: 10.1021/acs.analchem.9b05750. Epub 2020 Apr 6.
Charge is a fundamental property of a molecule, and precisely measuring it enables detection of the molecule and helps understand various chemical processes involving charge. Here we show a method to measure the charge of a single nanoparticle and binding of charged molecules to the nanoparticle using a conventional bright field optical microscope. The nanoparticle is tethered to an indium tin oxide surface with a polymer and driven into oscillation with an alternating electric field, which produces scattered light captured by a camera. The weak scattered light is separated from the intense bright field background using a Fourier transform filter, and the image contrast change provides the effective charge of the nanoparticle with precision of a few electron charges or less. This method allows us to detect DNA binding to the nanoparticles, demonstrating a simple method to detect and study molecules with a conventional optical microscope.
电荷是分子的基本属性，精确测量电荷可以实现对分子的检测，并有助于理解涉及电荷的各种化学过程。在这里，我们展示了一种使用传统明场光学显微镜测量单个纳米粒子电荷和带电荷分子与纳米粒子结合的方法。纳米粒子通过聚合物与氧化铟锡表面连接，并通过交流电场驱动进入振荡，从而产生被相机捕获的散射光。使用傅里叶变换滤波器从强明场背景中分离出微弱的散射光，图像对比度的变化提供了纳米粒子的有效电荷，精度可达几个电子电荷或更少。这种方法使我们能够检测 DNA 与纳米粒子的结合，展示了一种使用传统光学显微镜检测和研究分子的简单方法。
